NOTES AND ABSTRACTS. 



703 



dominates. Root-pruning should be done in October whilst the soil is 

 still warm. Advice as to the method is given. — C. W. D. 



Roridula, Some recent Observations on the Biology of. By 



R. Marloth, Ph.D., M.A., with a figure of the flowering branch of B. den 

 tata in the text (Ann. Bot, vol. xvii. No. lxv., p. 152 ; January 1903). — 

 This is a very interesting contribution to our knowledge of insectivorous 

 plants. The author points out that the two species of Roridula are the 

 only shrubby representatives of the order Droseracece that are known. 

 B. dentata grows to the height of 4 feet, while B. Gorgonias is a shrublet 

 12 to 15 inches high. In South Africa, in the districts where these plants 

 grow, branches are suspended in the houses for the purpose of catching 

 flies. The most remarkable points in this paper are in the statements 

 that an insect required for the pollination of the flowers is proof 

 against the secretion by which other insects are caught, and that a spider 

 is equally proof against it and lives by stealing from the plant. 



"When recently visiting one of the localities where B. dentata is 

 known to grow, viz. the valley above the Tulbagh waterfall, I noticed a 

 spider walking about on the bushes, and on examining the bushes more 

 closely I found that the spiders were quite numerous. They were all of 

 one kind, belonging to one genus, Syiuema (Crab-spiders). Dr. Purcell, 

 who kindly examined the specimens, is of the opinion that it is an 

 undescribed species. The crab-spiders spin no web, but wait for their 

 prey and pounce upon it whenever it comes near enough. This species 

 had selected the Boridula for its residence, and was evidently quite at 

 home there, for numerous little nests were hidden among the leaves, 

 some of which were empty and serving only as hiding-places for the 

 spiders, while others contained a large number of young spiders. 



" The surprising feature of the matter was that the spiders were able 

 to walk or run over the leaves without the slightest hindrance from the 

 sticky secretion of the tentacles. Whenever an insect was caught by a 

 leaf and began to hum or struggle, a spider in its neighbourhood would 

 dart from its nest and secure the prey. Hence it is evident that the 

 spider must be protected by some kind of varnish or grease against the 

 sticky fluid, for neither their legs nor their bodies adhere to it in the 

 slightest degree. Whether the same species of spider lives on any other 

 plant is not known, but it has evidently adapted itself to the Boridula, 

 and lives on the insect caught by the bush." 



While studying the structure of the flowers the author noticed that 

 the position of the anthers varied. He soon detected the cause of the 

 different position, for on irritating the " connective of the stamen " he 

 saw the anther swinging round with a jerk ejecting a little cloud of pollen. 

 This proved that the stamens of Boridula are irritable. 



He says : " This special contrivance showed that the fertilisation of 

 these flowers must be effected by insects ; but in spite of my watching 

 the shrubs for about an hour, I did not observe any visitor. The difficulty 

 of the case was to understand how an insect could be adapted to visiting 

 these flowers, for how could it escape being caught by the leaves or calyx- 

 lobes, unless it had learnt to avoid the danger in some special way ? 



" At last I found the solution of the problem, for I noticed a small 



